I don't think PG is making an empirical argument, it's based on intuition and then tries to just offer a few instances that are at least nominally consistent with the idea. Nate Silver recently said about Trump, "voters are much more tribal than I thought", and if you assume most voters don't know anything about candidates other than "it's a guy on the TV", they wouldn't respond to whether this guy was a yes man for Johnson or whatever, they just respond to who they like the most on an emotional level, and that's going to be whoever is the most charismatic during their campaign.